Abstract. Mobility particle size spectrometers often referred to as DMPS (Differential Mobility Particle Sizers) or SMPS (Scanning Mobility Particle Sizers) have found a wide range of applications in atmospheric aerosol research. However, comparability of measurements conducted world-wide is hampered by lack of generally accepted technical standards and guidelines with respect to the instrumental setup, measurement mode, data evaluation as well as quality control. Technical standards were developed for a minimum requirement of mobility size spectrometry to perform long-term atmospheric aerosol measurements. Technical recommendations include continuous monitoring of flow rates, temperature, pressure, and relative humidity for the sheath and sample air in the differential mobility analyzer.We compared commercial and custom-made inversion routines to calculate the particle number size distributions from the measured electrical mobility distribution. All inversion routines are comparable within few per cent uncertainty for a given set of raw data.Furthermore, this work summarizes the results from several instrument intercomparison workshops conducted within the European infrastructure project EUSAAR (European Supersites for Atmospheric Aerosol Research) and AC-TRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) to determine present uncertainties especially of custom-built mobility particle size spectrometers. Under controlled laboratory conditions, the particle number size distributions from 20 to 200 nm determined by mobility particle size spectrometers of different design are within an uncertainty range of around ±10 % after correcting internal particle losses, while below and above this size range the discrepancies increased. For particles larger than 200 nm, the uncertainty range increased to 30 %, which could not be explained. The network reference mobility spectrometers with identical design agreed within ±4 % in the peak particle number concentration when all settings were done carefully. The consistency of these reference instruments to the total particle number concentration was demonstrated to be less than 5 %.Additionally, a new data structure for particle number size distributions was introduced to store and disseminate the data at EMEP (European Monitoring and Evaluation Program). This structure contains three levels: raw data, processed data, and final particle size distributions. Importantly, we recommend reporting raw measurements including all relevant instrument parameters as well as a complete documentation on all data transformation and correction steps. These technical and data structure standards aim to enhance the quality of long-term size distribution measurements, their comparability between different networks and sites, and their transparency and traceability back to raw data.
Particle mobility size spectrometers often referred to as DMPS (Differential Mobility Particle Sizers) or SMPS (Scanning Mobility Particle Sizers) have found a wide application in atmospheric aerosol research. However, comparability of measurements conducted world-wide is hampered by lack of generally accepted technical standards with respect to the instrumental set-up, measurement mode, data evaluation as well as quality control. This article results from several instrument intercomparison workshops conducted within the European infrastructure project EUSAAR (European Supersites for Atmospheric Aerosol Research). Under controlled laboratory conditions, the number size distribution from 20 to 200 nm determined by mobility size spectrometers of different design are within an uncertainty range of ±10% after correcting internal particle losses, while below and above this size range the discrepancies increased. Instruments with identical design agreed within ±3% in the peak number concentration when all settings were done carefully. Technical standards were developed for a minimum requirement of mobility size spectrometry for atmospheric aerosol measurements. Technical recommendations are given for atmospheric measurements including continuous monitoring of flow rates, temperature, pressure, and relative humidity for the sheath and sample air in the differential mobility analyser. In cooperation with EMEP (European Monitoring and Evaluation Program), a new uniform data structure was introduced for saving and disseminating the data within EMEP. This structure contains three levels: raw data, processed data, and final particle size distributions. Importantly, we recommend reporting raw measurements including all relevant instrument parameters as well as a complete documentation on all data transformation and correction steps. These technical and data structure standards aim to enhance the quality of long-term size distribution measurements, their comparability between different networks and sites, and their transparency and traceability back to raw data
Light duty vehicle emissions legislation requires calibration and validation of Condensation Particle Counters (CPCsHowever, tests performed at JRC after the workshop found much lower counting efficiencies for tetracontane particles (almost 0 at 23 nm) and variable results for NaCl (0.6 or lower for 23 nm) indicating the importance of the generation method and the thermal treatment of the generated aerosol. Measurement issues including calibration against an electrometer or a reference CPC, the effect of multiply charged particles on counting efficiencies, stability, repeatability, reproducibility and comparability of CPCs and electrometers of different manufacturers were also investigated.
ZUSAMMENFASSUNG:Es wird uber die Strukturuntersuchungen vou oligomeren und polymeren Siloxanen mit verschiedenen Substituenten durch 29Si-Hochauflosungs-Kernresonanzspektroskopie berichtet. Iufolge der erreichten hohen Auflosung gelingt es nicht nur bei entsprechender Konzentration End-, Mittel-und Verzweigungsgruppen zu unterscheiden, sondern auch die Kopplungskonstante J(29Si-C~lryl-H) bei einigen der untersuchten Verbindungen aus dem 2%-KMR-Spektrum zu bestimmen. Die von der Zahl der an Silicium gebuudenen Methylgruppen abhangige Zahl der Linien des 2%-Multipletts gestattet ebenfalls eine Unterscheidung der verschiedenen funktionellen Gruppen. Ferner wurden einige technische Silikone vermessen. SUMMARY:Results of structural investigations of oligomeric and polymeric siloxanes with different substituents by high resolution 29Si-NMR spectroscopy are reported. It is possible to distinguish end-, middle-, and branching groups and to measure coupling constants J(29Si-C~lr~l-H) by 29Si-NMR-spectroscopy of some of the investigated substances. The number of the lines of the 2%-multiplet depends on the number of the methyl groups bonded to Si. This means that another possibility exists for determination of the different functional groups. 2%-NMR-spectra of some technical silicones also have been obtained.
An increased number of studies are focusing on the detection and investigation of nanometer-sized particles. One important tool is the Scanning Mobility Particle Sizer (SMPS). In the case of dynamic processes like nucleation events, the lower detection threshold as well as the measurement time are important system parameters. The limiting factors which determine the accuracy of the SMPS are the high voltage accuracy under dynamic conditions and knowledge of the response function of the detector. Especially the quality of the sizing depends on the accuracy of applied voltages in the differential mobility analyzer. High accuracy of the applied voltage as a function of time during fast scanning is required. Short scan times additionally yield a broadening and smearing of the measured size distribution. Here, the performance of the Nano-SMPS using the new TSI classifier (TSI 3082) in combination with either the nano water condensation particle counter (TSI 3788) or the ultrafine condensation particle counter (TSI 3776) was investigated. The focus of this work is the performance of the system at the lower detection limit as a function of the scan time. Fast scan times as short as three seconds were tested and compared to quasi-stationary measurements. The reproducibility of the aerosol size distribution and number concentration for different distributions and materials was investigated. The tested substances included different proteins (myogobin, ubiquitin, ferritin, albumin), sucrose and polystyrene latex reference particles. The sizing reproducibility and accuracy for all tested scan times was within 3%. This is only possible, by determining the delay time precisely. In addition, the limitations in size resolving power due to smearing and broadening resulting from fast scan times were investigated and quantified. The measured total number concentration was captured with a precision of ±3% for all tested scan times. The determination of the absolute concentration for this size range was not considered and remains a challenge for future studies, as diffusion losses, charging probability and CPC counting efficiency are critical issues.
Measurement techniques which allow the detection of airborne nanoparticles are of great interest for e.g. exposure monitoring and quality control during nanoparticle production. An increasing number of commercial devices use a unipolar diffusion charger to charge the particles and determine the nanoparticle concentration and sometimes size. The analysis however may be biased by the presence of large particles. We therefore developed a preseparator that removes particles larger than 450 nm, i.e the minimum in the range of particle lung deposition curves, but only causes a low pressure drop. The preseparator uses a total flow rate of 2.5 L/min and consists of two stages. The first stage is a virtual impactor that removes particles larger than approximately 1 µm with a minor flow of 1 L/min. Particles above 450 nm are removed from the remaining 1.5 L/min in the cyclone of the second stage. The combination of a cyclone with a virtual impactor was shown to reduce the pressure drop of the preseparator from 8.1 to 5.6 kPa compared with a cyclone alone and improve the sharpness of the separation curve for cut-off diameters around 450 nm. Furthermore the virtual impactor extends the cleaning intervals of the preseparator, because large particles are no longer deposited in the cyclone. Eventually the preseparator was tested with an opposed flow diffusion charger and it was shown that particle charging is not affected by the pressure drop.
Es werden zwei neue Verfahren zur Herstellung von z.T. bekannten Trihalogensilanthiolen (II) beschrieben.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.